Pedicle screw for intervertebral support elements

ABSTRACT

The pedicle screw ( 1 ) for intervertebral support elements ( 3 ) consists of a shaft ( 10 ) and a head ( 2 ) comprising at least two parts ( 20, 22 ). The head is formed as a securing means for at least one support element ( 3 ). Each support element consists of a piece of a cable-like band ( 31 ) and a cylindrical support body ( 30 ) with an axial lumen ( 31″  containing the band. The band is securable outside end surfaces ( 32 ) of the support body in the head. The head is formed with a contact surface ( 23 ) via which a pressure stress can be exerted on the support body in the band direction, and indeed using the band and in cooperation with a further pedicle screw. A part ( 20 ) of the head ( 2 ), which is firmly connected to the shaft ( 10 ) at the one end of the latter, contains a base groove ( 21 ) which is oriented transversally to the shaft and into which the part of the band ( 31 ) to be secured or a connecting piece ( 292 ) which contains the band can be introduced during the securing of the support element ( 3 ) by means of a translatory movement in the direction of the shaft and fixed there.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/565,825, filed on Dec. 1, 2006; which is a continuation of U.S.application Ser. No. 09/956,055, filed on Sep. 18, 2001; which claimspriority to European Patent Application No. 00810845.8, filed on Sep.18, 2000, which are all incorporated herein by reference.

TECHNICAL FIELD

The invention relates to a pedicle screw for intervertebral supportelements.

BACKGROUND

Invasive treatment methods are known for the stabilization of spinalcolumns in which bone bridges are made to grow between adjacentvertebral bodies using implants. Stiffening fusions of the adjacentvertebrae result through the bone bridges. In addition to stiffeningoperations of this kind a treatment method for stabilizing by means ofan implant system is also known in which no fusion arises, but rather amobility is preserved between adjacent vertebrae. This implant systemcomprises pedicle screws and intervertebral support elements which areimplanted during the operation from the back. Each pedicle screw has ahead which is formed as a ring. In each case two pedicle screws arescrewed in a vertebral body through the pedicle passages of thevertebra. The support elements are secured at the screw heads. Twosupport elements which are arranged in parallel between adjacentvertebrae form a dynamic supporting of these vertebrae. Thevertebrae—with the exception of the lowermost lumbar vertebra—can ineach case also be connected at the same pedicle screws to an upwardlyand a downwardly adjacent vertebra through two pairs of supportelements.

Each support element consists of a piece of a cable-like band and acylindrical support body which is elastically yielding. A rigid materialcan also be used for individual support bodies in order to stiffen thespinal column at individual locations. The band is drawn in an axiallumen of the support body. The intervertebral support elements aresecured at the pedicle screws using the band. In this the bands must bedrawn through through the ring heads. The drawing in of the band is anoperation step which is difficult to carry out.

SUMMARY

The object of the present invention is to create, for dynamic vertebrasupporting, a pedicle screw for intervertebral support elements forwhich the securing of the support element at the pedicle screw, whichmust take place during the surgical operation, can be carried out moreeasily.

The pedicle screw for intervertebral support elements consists of ashaft and a head which comprises at least two parts. The head is formedas a securing means for at least one support element. Each supportelement consists of a piece of a cable-like band and a cylindricalsupport body with an axial lumen which contains the band. The band canbe secured outside end surfaces of the support body in the head. Thehead is formed with a contact surface via which a pressure stress can beexerted on the support body in the band direction, and indeed using theband and in cooperation with a further pedicle screw. A part of thehead, which is firmly connected to the shaft at the one end of thelatter, contains a base groove which is oriented transversally to theshaft and into which the part of the band to be secured or a connectingpiece which contains the band can be introduced during the securing ofthe support element by means of a translatory movement in the directionof the shaft and fixed there.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in the following in more detail withreference to the drawings. Shown are:

FIG. 1 a lumbar vertebra showing the position of two pedicle

FIG. 2 two pedicle screws with an intervertebral support element for twofor two adjacent vertebrae,

FIG. 3 an outline illustration of adjacent lumbar vertebrae showing theposition of two implanted support elements,

FIG. 4 the head of a pedicle screw in accordance with the inventiontogether with a support element,

FIG. 5 a second embodiment of the head with a T-shaped groove-stone,

FIGS. 6, 7 two heads in which disc-shaped parts are arranged between thesupport element and the head,

FIG. 8 a head with a connector,

FIG. 9 a variant of the connector of FIG. 8,

FIG. 10 a head with a sleeve part

FIG. 11 a further embodiment of the head with a connector and

FIG. 12 a cross-section through the head of the embodiment in accordancewith FIG. 10.

DETAILED DESCRIPTION

A lumbar vertebra 9 in accordance with FIG. 1 consists of a vertebralhole 90, a vertebral body 91 and a vertebral arch 92 which comprises twopedicles 93, two transverse processes 94, a spine 95 of a vertebra andarticular processes 96. The positions of two pedicle screws 1 in theimplanted state are indicated in chain-dotted lines. In these positionsthe heads 2 of the pedicle screws 1 are located directly at the outerside of the pedicles 93 between the transverse processes 94 and thearticular processes 96. FIG. 2 shows two pedicle screws 1, which areprovided for two adjacent vertebrae 9 and between the heads 2 of which,which are formed as rings, an intervertebral support element 3 isarranged. Shafts 10 of the pedicle screws 1 are screwed in into thevertebrae 9. The heads 2 have notches 4 laterally which are required forthe implanting and orientation of the pedicle screws 1 by means of aninstrument. The support element 3 consists of a piece of a cable-likeband 31 and a cylindrical support body 30 in which the band 31 iscontained in an axial lumen 31′. The band 31 is secured outside of endsurfaces 32 of the support body 30 in each case in the heads 2 of thepedicle screws 1 with a setting screw 22. The heads 2 are provided withplanar contact surfaces 23 via which a pressure stress can be exerted onthe support body 30 in the band direction via their end surfaces 32,with the tension force required for this being produced using the band31 and in cooperation with the pedicle screw 1 of the adjacent vertebra9.

An outline drawing with two adjacent lumbar vertebrae 9 is shown in FIG.3. The positions of two implanted support elements 3 are indicated.

The pedicle screw 1 in accordance with the invention differs from theknown pedicle screw through a specially formed head 2. The supportelement 3 can be laid in into the latter by means of a translationalmovement in the direction of the shaft 2, so that the support element 3can be fixed in the head without a drawing in of the band 31 into aneye-like securing means being required.

A first embodiment of the head 2 of a pedicle screw 1 in accordance withthe invention is illustrated in FIG. 4 together with a support element3. A part 20 of the head 2 which comprises two lugs 20 a and 20 b andwhich is firmly connected to the shaft 10 contains a base groove 21which is oriented transversely to the shaft 10 and a thread 24. A partof the band 31 which is to be secured is inserted into the base groove21 during the securing of the support element 3 and is fixed with ascrew 22. The base groove 21 has a shape which corresponds to the shapeof the band in such a manner that the base groove is formedcomplementarily in the insertion region. An edge region 21′ of the basegroove 21 can—in order to prevent a damage to the inserted band 31—beformed in such a manner that the base groove 21 widens in the directiontowards the contact surface 23.

The embodiment of FIG. 4 is a first example of a pedicle screw inaccordance with the invention, in which the lugs 20 a, 20 b, which formflanks of the base groove 21, have depressions 24 on their inner sidesinto which a securing part, namely the screw 22, can be firmly anchoredby means of a form lock. After the production of the form lock the lugs20 a, 20 b are advantageously elastically spread apart somewhat by thesecuring part 22, so that the position of the latter is additionallyfixed as a result of an increased adhesive friction and thus of a forcelock.

A second example is shown in FIG. 5, in which the lugs 20 a, 20 b havegroove-like depressions 24 a on their inner sides. A T-shapedgroovestone 25 with lateral ribs 25 a is pushed in between the grooves24 a after the insertion of the band 31—cf. FIG. 5—and for fixing theband 31 a setting screw 22—cf. FIG. 5—is screwed into a bore in thegroove-stone 25 with inner thread 250.

FIGS. 6 and 7 show in each case a head 2 in which a disc-shaped part 26is arranged between the support element 3 and the head 2. The head 2 inFIG. 6 comprises a core part 20 and at least one disc-shaped part 26which forms the contact surface 23 to the cylindrical support body 30 ofthe support element 3 on the one side and which forms a contact surface261 to the core part 20 on the other side. The surface of the core part20 is made spherical. The contact surface 261 to the core part 20 of thedisc-shaped part 26 is made in the shape of a spherical sectioncorresponding to the shape of the core part 20. The disc-shaped part 26is applied together with the support body 30 to the band 31, with theband 31 being drawn into the bore 260. This drawing in of the band 31 iscarried out prior to the implanting of the support element 3 outside thebody of the patient to be operated on.

The head 2 in FIG. 7 comprises a core part 20 which has at each end ofthe groove 21 an elevation 262 which is formed to fit complementarily toa groove 263 of the disc-shaped part 26 (ridge-groove form lock). Thegroove 263 can be pushed onto the elevation 262 in the direction ofthe—shaft 10. As was already the case in the example of FIG. 6, the part26 is applied to the band 31 prior to the implanting.

FIG. 8 shows a head 2 with a core part 20 and with a connector 27 whichis a sleeve-like part and the inner space of which has a square profilewhich is formed by planar surfaces. The core part 20 is tightly enclosedby the connector 27, so that a spreading open of the lugs 20 a, 20 bduring the screwing in of a screw 22 (see FIG. 10) into the thread 24 isprevented.

FIG. 9 shows a variant 27′ of the connector 27 of FIG. 8. This connector27′ is made longer in the direction of the groove 21 or of the bore 270and contains a bore with inner thread 272. The band 31 can additionallybe fixed below the threaded bore 272 with a second screw 22.

FIG. 10 shows a head 2 with a sleeve part 28 and with a core part 20which is firmly connected to the one end of the shaft 10. The screw-cappart 28 is displaceable along the entire shaft 10 up to the named shaftend. In this the thread 24 comes to lie over the groove 21 so that thescrew for the securing of the band 31 can be screwed into the thread 24.

FIG. 11 shows a further embodiment of the head 2 with a connector 29.The band 31 can be secured in the connector 29 in a bore 293. During theoperation the connector 29, which contains the band 31, is placed ontothe core part 20 of the head 2, with a connecting piece 292 of theconnector 29, which has a prismatic shape, being laid in into thecorresponding complementarily shaped groove 21. The securing between theconnector 29 and the core part 20 can be produced for example with twoscrews. The non-illustrated screws are inserted through bores 291 a ofthe connector 29 and are screwed tight in threaded bores 291 b of thecore part 20.

The embodiments in accordance with FIGS. 6 and 10 permit a so-called“polyaxiality” in the fixing of the support body 30 at the pediclescrews 1. The “polyaxiality” relates to the axis of the shaft 2; in allother body 30, which is given by the axis of their lumens 31′. The term“polyaxiality” is intended to mean that the angle between the two axisdirections is not fixed in advance, but can vary within a certainangular range. This will be explained for the embodiment in accordancewith FIG. 10 in more detail with reference to FIG. 12: FIG. 12 shows across-sectional illustration of the pedicle screw head 20 with thesleeve part 28, the inner surface 280 of which is a partial region of aspherical surface. The head 20 is made correspondingly spherical, sothat it can be laid in into the sleeve part 28 in different positions.The axis of the shaft 10 has a main direction z perpendicular to thedirection x of the support body 30 (x is perpendicular to the plane ofthe drawing). The shaft axis can deviate with respect to this maindirection z by an angle (.phi. This angle .phi. has a maximum value.phi.sub.max which amounts to 10.degree. or even more, but which is lessthan 15.degree. The angle .phi. can vary in the region of a cone aboutthe main direction z, with the half opening angle of this cone amountingto phi.sub.max. Corresponding remarks also hold for the embodiment inaccordance with FIG. 6. The system for the vertebral support which canbe produced with the pedicle screws in accordance with FIGS. 6 and 10 iseasier to implant thanks to the “polyaxiality”.

Longitudinal components comprising support elements are anchored invertebrae with pedicle screws, with a dynamic stabilizing of thevertebrae being producible thanks to an elastic yielding of the supportelements. The pedicle screws in accordance with the invention permit ahead feeding of the longitudinal components. In the head feeding thelongitudinal components are laid in into the heads of the pedicle screwsin that merely a translational movement in the direction of the shaft inthat merely a translational movement in the direction of the shaft needbe carried out. Through a simple insertion of this kind the operationtechnique is obviously substantially simplified with respect to theolder treatment methods, in which the bands of the support elements mustbe drawn in into the screw heads, which are formed in ring shape.

1. A dynamic stabilization system for a spinal column, the dynamicstabilization system comprising: a first vertebral fastener configuredto be secured to a first vertebra, the first vertebral fastenerincluding a head defining a channel; a support element including aspacer having a bore extending therethrough and a flexible member sizedto insert through the bore of the spacer; and a first member with afirst portion positionable between a first surface of the spacer of thesupport element and a surface of the head of the first vertebralfastener, and a second portion positionable within the channel of thefirst vertebral fastener.
 2. The dynamic stabilization system of claim1, wherein the first member includes a third portion, wherein the firstportion of the first member is positionable on a first side of the headof the first vertebral fastener and the third portion of the firstmember is positionable on a second side of the head of the firstvertebral fastener opposite the first side of the head of the firstvertebral fastener.
 3. The dynamic stabilization system of claim 1,wherein the first member is configured to space the support element fromdirect contact with the head of the first vertebral fastener.
 4. Thedynamic stabilization system of claim 1, wherein the first member ispositionable in abutment with the spacer.
 5. The dynamic stabilizationsystem of claim 1, wherein the first member is securable to the head ofthe first vertebral fastener with one or more threaded screws.
 6. Thedynamic stabilization system of claim 1, wherein the first memberincludes a bore extending therein sized to receive the flexible member.7. The dynamic stabilization system of claim 1, wherein the first memberincludes a bore extending therethrough sized to receive the flexiblemember.
 8. The dynamic stabilization system of claim 1, wherein thefirst member is a connector.
 9. The dynamic stabilization system ofclaim 1, wherein the spacer is a support body.
 10. The dynamicstabilization system of claim 1, wherein the first member has alongitudinal axis and the second portion of the first member ispositionable in the channel of the first vertebral fastener bytranslation of the first member in a direction generally transverse tothe longitudinal axis of the first member.
 11. The dynamic stabilizationsystem of claim 1, wherein the first vertebral fastener includes athreaded shaft portion having a longitudinal axis; and wherein thesecond portion of the first member is positionable in the channel of thefirst vertebral fastener by translation of the first member in adirection generally parallel to the longitudinal axis of the threadedshaft portion of the first vertebral fastener.
 12. The dynamicstabilization system of claim 1, further comprising: a second vertebralfastener configured to be secured to a second vertebra, the secondvertebral fastener including a head defining a channel; and a secondmember with a first portion positionable between a second surface of thespacer of the support element and a surface of the head of the secondvertebral fastener, and a second portion positionable within the channelof the second vertebral fastener.
 13. The dynamic stabilization systemof claim 12, wherein the second member includes a third portion, whereinthe first portion of the second member is positionable on a first sideof the head of the second vertebral fastener and the third portion ofthe second member is positionable on a second side of the head of thesecond vertebral fastener opposite the first side of the head of thesecond vertebral fastener.
 14. The dynamic stabilization system of claim12, wherein the support element is positionable between the head of thefirst vertebral fastener and the head of the second vertebral fastener.15. The dynamic stabilization system of claim 12, wherein the secondmember is configured to space the support element from direct contactwith the head of the second vertebral fastener.
 16. The dynamicstabilization system of claim 12, wherein the second member ispositionable in abutment with the spacer.
 17. The dynamic stabilizationsystem of claim 12, wherein the second member is securable to the headof the second vertebral fastener with one or more threaded screws. 18.The dynamic stabilization system of claim 12, wherein the second memberincludes a bore extending therein sized to receive the flexible member.19. The dynamic stabilization system of claim 12, wherein the secondmember includes a bore extending therethrough sized to receive theflexible member.
 20. The dynamic stabilization system of claim 12,wherein the second member is a connector.
 21. The dynamic stabilizationsystem of claim 12, wherein the second member has a longitudinal axisand the second portion of the second member is positionable in thechannel of the second vertebral fastener by translation of the secondmember in a direction generally transverse to the longitudinal axis ofthe second member.
 22. The dynamic stabilization system of claim 12,wherein the second vertebral fastener includes a threaded shaft portionhaving a longitudinal axis; and wherein the second portion of the secondmember is positionable in the channel of the second vertebral fastenerby translation of the second member in a direction generally parallel tothe longitudinal axis of the threaded shaft portion of the secondvertebral fastener.